Patent GB-289773-A (GB)
Title: Improvements in or relating to switches for use in telephone or like systems
IPC: H04Q3/00
Filed: 1928-04-20
Abstract: 289,773. Associated Telephone & Telegraph Co., (Assignees of Wicks, J.). April 30, 1927, [Convention date]. Automatic exchange selectors and associated apparatus.-A two-directional switch for use with vertical or horizontal bare wire multiple comprises two carriages movable at right-angles to one another in turn by springs controlled by an escapement device. A steel band 8, Fig. 1, is unwound by the escapement device 4 controlled by a magnet 1, and is returned by a release magnet 50. The first operating digit allows the main carriage 14 to move to the right, after which a magnet 26 is operated to lock carriage 14 and to unlock wiper carriage 10 which then moves the wiper into the bank. Selector and connector circuits are described below. Switch construction. A lever 16, pivoted to a bracket 15 on carriage 14, has its lower end, Fig. 2, hooked to engage normally the hooked extension 11 of carriage 10, while its upper end supports a pivoted arm 17 against a spring 41. When the escapement lever 4, operated by magnet 1, allows the band 8 to unwind, carriage 14 is drawn to the right by a spring 43 until the wipers 44, 45, 46 are opposite the required group of terminals. Magnet 26 is then operated to oscillate a pivoted plate 29, which shifts lever 16 and also a lever 12, 13 pivoted to the extension 11 to release the wiper carriage, and also to allow the locking arm 17 to rotate, the end of lever 16 entering a slot 40 therein. A projection 17<1> on lever 17 engages a tooth 19 on a locking-plate 18 to loch carriage 14 against further movement. Further operation of the escapement allows a spring 39 to draw the wiper carriage downwards so that the wipers engage wires such as 47, 48, 49, Fig. 1. When release magnet 50 operates, the band 8 is wound up first withdrawing the carriage 10. Since magnet 26 was only transiently operated, the lever 12 will have returned to normal, so that when the wiper carriage reaches normal, lever 12 will shift lever 17 to unlock carriage 14 and to release lever 16 which locks the wiper carriage. Carriage 14 is then returned until it separates off-normal contacts 56 to release magnet 50. Selector and connector circuits; setting-up connection. Line and release relays 5, 10 energize and form a circuit [earth 9, 11, 28, lower winding of 15, 21, 48, 25, 30, battery] in which relay 15 energizes, but not relay 25 or stepping magnet 30. When the next digit is dialled, armature 7 is chattered to operate magnet 30 and relay 25 by direct earth from 46, off-normal springs 9. 27, 29 opening. Relay 15 holds up over its upper winding during impulsing. At the end of the digit, 25 releases, and switching magnet 35 operates to earth at 29, looking the main carriage, unlocking the wiper carriage, and forming a parallel self-interrupting circuit for magnet 30 which steps the wipers to the first trunk contacts. If the trunk is busy, switching relay 43 is shorted by low-resistance earth on test contact 39 and magnet 30 again steps the switch. On reaching an idle trunk, 45 operates over its high and low resistance windings in series, and then shorts its high-resistance winding at 29 to busy the trunk, releasing the magnets at 47. Relay 50 operates in series with 45 and relay 60 and stepping magnet 66 are connected to a bridge over the lower winding of relay 15, which remains energized, but prevents 60, 66 pulling up. The next digit operates armature 7 as before to short the lower winding of 15 intermittently so that magnet 66 is impulsed, relay 60 being energized during the digit. Between the digits, switching magnet 90 operates to earth at off-normal springs 56. The second digit similarly operates magnet 66. Wanted line busy. Busy relay 70 operates before relay 60 releases and locks up to earth at 52. Busy tone is sent back from 67. Ringing and completion of connection. Battery on test contact 95 operates switching relay 80 over its upper winding to earth at 52. 80 locks up over its lower winding, releases relay 15 and completes the ringing circuit over the upper winding of relay 75. When the wanted subscriber replies, 75 operates and completes the connection, back-bridge relay 20 energizing. Release. Release is controlled by calling subscriber. Relays 5, 10 release, releasing 45 at 13, and forming a homing circuit for release magnet 40 to earth at 29. The switch is busied during release at off-normal springs 27. Release of 50 releases 75, 80 at 52 and release magnet 64 homes the connector.